The proposed research plan involves the development and application of a new method for measuring oxygen concentration profiles in tissues and living cells. This technique is based on the observation that the fluorescence emission of pyrenebutyric acid is quenched by oxygen. The main approach will be to monitor the fluorescence intensity and lifetime profiles of various biological materials, treated with pyrenebutyrate, using microscopic techniques. The specific research objectives include: (1) Development of better systems of data acquisition including fiber optics probes and measurements of fluorescence lifetimes as well as intensities; (2) a determination of oxygen concentration gradients within tissue slices and within cells and comparison with various theories of oxygen transport; (3) application of this technique to the study of physiological function of the exposed intact carotid body and brain of the cat in association with measurements of the redox state of the respiratory chain; (4) application of this technique to the study of oxygen concentration gradients within capillary networks. BIBLIOGRAPHIC REFERENCES: Longmuir, I.S. and Knopp, J.A., "Colloquium on Oxygen and Physiological Function." FASEB, 1976. (In press.) Knopp, J.A. and Longmuir, I.S., "Oxygen Quenching of the Fluorescence of Pyrenebutyric Acid." PHOTOPHYSICS (John B. Birks, ed.), pp. 84-91, John Wiley and Sons, Ltd., Sussex, England. 1976.